Hooks or clips that grip the inverted "T" grid rail of suspended ceilings are well known as devices for suspending signs and other weighted objects from suspended tile ceilings. Although these devices are useful for some purposes, there are a number of drawbacks to such means of attaching signs and other objects.
Suspended ceiling clips, such as the clip described in U.S. Pat. No. 4,073,458 ("the '458 patent"), utilize a "U" design attached to the lower edge of a grid rail. The '458 patent hanger clip is formed from a thin strip of metal with a U-bend portion formed in approximately the middle of the strip, that clips onto the horizontal ledge of the overhead beam, and lower end for attaching articles to. The '458 patent also uses a vertical portion extending from the upper end of the "U" clip which fits between the vertical leg of the overhead beam and a ceiling panel installed on that beam to hold the clip in position.
The device described in the '458 patent, although useful in some situations, may require the "U" clip conform to the dimensions of a specific grid rail. In the case of many present day suspended tile ceilings, "U" clips may be incapable of gripping grid rail ledges that can be 1/4 inch or less in width, and that may have rounded or beveled edges and surfaces for aesthetic as well as functional qualities, as such narrow, beveled or rounded rails permit ceiling tiles to fit tighter, resulting in superior sound and heat insulation performance. "U" clips are easily dislodged from such grid rails, if they can be affixed to such rails at all.
If the grid rail ledge is wide, or the weight suspended from it is heavy, the legs of the clip may be pulled apart by the weight suspended from the lower portion of the clip, so as to no longer permit the clip to grip the grid rail.
Another disadvantage of the use of such clips is that in order for the suspended item to be held horizontally stable, at least two clips must generally be used. As suspended tiles may be extremely lightweight, the use of such clips to suspend heavy items from "T" rails can cause grid rails to bend or deform in the case of a clip that fails to distribute the weight of suspended items along the greatest possible surface area of the grid rail ledge. Low-strength rails may also twist, causing the clip to become dislodged and the object suspended below to fall.
Further, as the object is suspended below such "U" clips via wire, chain, or other means, it is more likely that an object will catch on an upper edge of the sign or object, thereby dislodging the clips from the grid rail. Clips can become dislodged by horizontal stress if they inflexibly grip a particular location on a grid rail. Finally, clips can deform, scratch or otherwise deface exposed lower surface of the grid rail.
Similarly, U.S. Pat. No. 4,223,488 ("the '488 patent") teaches a ceiling hanger adapted to be removably installed on tile ceiling grid rails; the hanger includes a plate having a U-shaped end portion embracing one edge of the grid rail, a midportion underlying the grid rail, and a retaining clip embracing the opposite edge of the grid rail. Advertisements or objects are to be hung from hooks or fasteners below the clips. The device described in the '488 patent, has limitations similar to those found in other grid rail clips.
Clips may offer insufficient resistance to a variety of anticipated and unanticipated dynamic stress situations. Grid rail clips, hooks, and other fastening means may also provide no satisfactory means to suspend a sign or other object over the center of a ceiling tile, as clips must be fastened to opposing grid rails and wires strung between the clips. Should one of the clips becomes dislodged (particularly in the case of a metal sign), the object can swing into or fall on personnel or equipment. A danger that an object passing below becoming entangled in the suspended wires traversing the clips may also exist.
It would therefore be desirable to develop a locking, suspended ceiling grid rail sign and bracket that will overcome the shortcomings of other grid rail clips and hooks.